首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1641篇
  免费   9篇
电工技术   2篇
综合类   1篇
化学工业   91篇
金属工艺   5篇
机械仪表   3篇
建筑科学   7篇
能源动力   12篇
轻工业   121篇
水利工程   1篇
武器工业   1篇
无线电   28篇
一般工业技术   42篇
冶金工业   1289篇
原子能技术   6篇
自动化技术   41篇
  2022年   4篇
  2020年   5篇
  2019年   4篇
  2017年   3篇
  2016年   11篇
  2015年   5篇
  2014年   8篇
  2013年   8篇
  2012年   10篇
  2011年   14篇
  2010年   10篇
  2009年   9篇
  2008年   6篇
  2007年   10篇
  2006年   10篇
  2005年   13篇
  2004年   5篇
  2003年   14篇
  2002年   10篇
  2001年   12篇
  2000年   5篇
  1999年   45篇
  1998年   419篇
  1997年   267篇
  1996年   165篇
  1995年   84篇
  1994年   80篇
  1993年   103篇
  1992年   16篇
  1991年   19篇
  1990年   15篇
  1989年   12篇
  1988年   10篇
  1987年   14篇
  1986年   19篇
  1985年   21篇
  1984年   7篇
  1983年   7篇
  1982年   12篇
  1981年   9篇
  1980年   9篇
  1978年   8篇
  1977年   26篇
  1976年   59篇
  1975年   7篇
  1974年   3篇
  1973年   10篇
  1972年   6篇
  1971年   5篇
  1967年   4篇
排序方式: 共有1650条查询结果,搜索用时 15 毫秒
101.
OBJECTIVES: The association of anti-HBs immunoglobulins and anti-HBV vaccine could increase the immunogenicity of the latter. The aim of this prospective randomized trial was to compare the immunogenicity of anti-HBs vaccination and serovaccination in alcoholic patients with cirrhosis. METHODS: Alcoholic patients with cirrhosis were randomized in 2 groups: a) Vaccination group: 3 i.m. injections of GenHevac B followed by one booster at month 9; b) Serovaccination group: same vaccination schedule followed by one i.m. injection of anti-HBs immunoglobulins (500 IU). RESULTS: Twenty-five patients (17 males and 8 females, mean age 56 years) were included in the study: 13 received a vaccination and 12 received a serovaccination. After 12 months, the seroconversion rates were 69% and 67% in vaccination and in serovaccination groups, respectively. The predictive factors of non responsiveness were as following: Child B cirrhosis, low number of CD8, a high CD4/CD8 rate, the existence of HLA DR7 antigen, and the absence of HLA DR1 antigen. CONCLUSION: In alcoholic patients with cirrhosis, serovaccination does not increase the immunogenicity of anti-HBs vaccination and should not be recommended.  相似文献   
102.
103.
104.
105.
106.
Quantitative estimates of dust exposure in a diatomaceous earth (DE) mining and milling operation have been derived based on air sampling records for the period 1948-1988. A total of 6395 records was included in the analysis. Conversion of results obtained by particle counting, expressed as millions of particles per cubic feet (mppcf) of gravimetrically from a filter cassette and expressed as mg m-3 total, were converted to mg m-3 respirable dust using a conversion factor derived from data obtained during the same periods at the plant. Conversion factors were calculated as the average difference of means on the log scale in order to provide stable and consistent conversions and as a ratio of arithmetic means so that the results could be compared with similar studies. After converting the available data to mg m-3 respirable dust, geometric mean (geometric standard deviation) concentrations were 0.37 (2.43) during the 1950s and 0.17 (2.35) during later periods. Exposures were estimated using two linear models, one estimating the changes in concentration over time, and the other providing job-specific mean exposures during the more recent period. Extrapolation of the estimates to periods prior to the availability of any data was done using a subjectively-determined scaling factor. The average estimated respirable dust concentrations for 135 jobs were 3.55 (+/-1.25), 1.37 (+/-0.48), 0.47 (+/-0.16) and 0.29 (+/-0.10) mg m-3 prior to 1949, 1949-1953, 1954-1973 and 1974-1988, respectively. Despite the limitations of the available data, the estimation procedures used are expected to provide reasonable quantitative estimates of silica-containing dust exposure for subsequent exposure-response analyses.  相似文献   
107.
Leakfree oscillating positive-displacement pumps – state of the art and trends of development . Leak- and maintenance-free oscillating positive-displacement pumps are very important for avoiding pollution and improving the reliability of plants. Technical progress in the field of hydraulic diaphragm- and tube-pumps for high pressures are explained. The actual data (pressure, efficiency, temperature) and experience with different fluids are surveyed. The various hydraulic control systems, the diaphragm design, and methods for rupture-control are compared. Further development trends are explained.  相似文献   
108.
The use of GaInNAs/GaAs as an alternative active material to InGaAs/GaAs for semiconductor disk lasers with Watt-level emission in the 1160?1210 nm wavelength range is reported.  相似文献   
109.
110.
Local electric defects may result in considerable performance losses in solar cells. Infrared (IR) thermography is one important tool to detect these defects on photovoltaic modules. Qualitative interpretation of IR images has been carried out successfully, but quantitative interpretation has been hampered by the lack of “calibration” defects. The aims of this study are to (i) establish methods to induce well‐defined electric defects in thin‐film solar cells serving as “calibration” defects and to (ii) assess the accuracy of IR imaging methods by using these artificially induced defects. This approach paves the way for improving quality control methods based on imaging in photovoltaic. We created ohmic defects (“shunts”) by using a focused ion beam and weak diodes (“interface shunts”) by applying a femto‐second laser at rather low power on copper indium gallium selenide cells. The defects can be induced precisely and reproducibly, and the severity of the defects on the electrical performance can be well adjusted by focused ion beam/laser parameters. The successive assessment of the IR measurement (ILIT‐Voc) revealed that this method can predict the losses in Pmpp (maximal power extractable) with a mean error of below 10%. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号